Flat bottom bag and method of making the same

ABSTRACT

This invention pertains to a flat bottom bag formed from flexible tubular material by making a pair of folds and a single seal. Specifically, the bag is formed by longitudinally folding the edge portions of a collapsed flexible tube inwardly to a superposed position on the main body portion thereof not extending beyond the longitudinal centerline of the tube. A transverse seam is then formed across the width of the tube adjacent the free edges at one of its ends securing together therealong the overlying plies comprising the folded tube. This completes the structure of a basic bag element from which a flat bottom bag can be formed. Several methods are taught as suitable for shaping the secured end of the above bag element to form the desired flat bottom structure. For example, by turning the bag element inside out and shaking out its folded edge portions a flat bottom bag is readily obtained.

United States Patent FLAT BOTTOM BAGAND METHOD OF MAKING THE SAME 5 Claims, 9 Drawing Figs.

Int. Cl B3lb 49/04 Field of Search 93/35, 35

Primary Examiner-Granville Y. Custer, Jr. Attorneys-Griswold 8L Burdick, Richard C. Waterman and Burke M. Halldorson ABSTRACT: This invention pertains to a flat bottom bag formed from flexible tubular material by making a pair of folds and a single seal. Specifically, the bag is formed by longitudinally folding the edge portions of a collapsed flexible tube inwardly to a superposed position on the main body portion thereof not extending beyond the longitudinal centerline of the tube. A transverse seam is then formed across the width of the tube adjacent the free edges at one of its ends securing together therealong the overlying plies comprising the folded tube. This completes the structure of a basic bag element from which a flat bottom bag can be formed. Several methods are taught as suitable for shaping the secured end of the above bag element to form the desired flat bottom structure. For example, by turning the bag element inside out and shaking out its folded edge portions a flat bottom bag is readily obtained.

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sum 2 BF 2 INVENTUR W/Y/l ai'n E. Shrum MWJJW HTTORNEY FLAT BOTTOM BAG AND METHOD OF MAKING THE SAME This application is a divisional application of my copending application Ser. No. 687,630, filed Dec. 4, 1967, now U'.S. Pat. No. 3,485,439, issued Dec. 23, I969.

DESCRIPTION OF THE INVENTION To increase the fill capacity in bag construction it has become customary to utilize a square or flat bottom bag structure. To this end a considerable number of bag designs have been proposed in the past. One of the most popular of these comprises forming inverse folds or gussets at the opposite edge portions of a tubular body and then securely closing one of the two ends of the tube, i.e., by forming a transverse seam across the width of the tube adjacent the end to be closed. While this method often produces a satisfactory bag, fabrication can be difficult since customarily the tube must be first in flated in order for forming members to press inwardly and form the gussets. The inflating of the bag in a continuous operation wherein a continuous length of tube is employed is not entirely a simple matter. Here it is not uncommon to provide complicated and specially designed apparatus to maintain the tube in an inflated condition during the period the gussets or inverse folds are being formed along its side or edge portions.

Accordingly, it is an object of the present invention to provide an improved method for forming flat bottom bags wherein only a couple folds need be made and a single seal effected to form a bag element from which a square or flat bottom bag can be easily obtained.

Another object of the present invention is to provide a method for fonning a flat or square bottom bag from continuous flexible tubular material wherein only a minimum of equipment is required and wherein the tube can be maintained in a collapsed condition during the forming of the bag.

Another object of the present invention is to provide a bag element or article inexpensively and easily fabricated and from which a square bottom bag can be readily obtained by a single shaping step.

Yet another object of the present invention is to provide an improved square bottom bag wherein the raw or free edges adjacent the seam at the closed end of the bag are hidden within the confines thereof to provide a flat bottom bag easily fabricated and esthetically appealing for particular uses, as,

for example, pouches in which expensive articles can be more readily merchandized.

Briefly then, this invention contemplates an improved method for forming a flat bottom bag from tubular material wherein a minimum of equipment is required. Basically, only a couple of folds and a single seam need be made to provide a basic bag element from which a square or flat bottom bag can be readily obtained. Specifically, the two joined edge portions of a flexible tube are longitudinally folded inwardly to a superposed position on the main body portion of the tube short of its longitudinal center line. A transverse seam is then efi'ected across the width of the folded tube at one end thereof secdi'itig together therealong the overlying plies comprising the folded tube, and thereby completing the construction of the basic bag element desired. The seamed end of the bag element can then be shaped by one of several different methods to provide a flat bottom bag. In one method, the bag element is turned inside out and the flat bottom is shaken out. Here the free or raw edges adjacent the transverse seam are placed within the confines of the bag such that its general or overall appearande is enhanced. By again turning the above obtained bag inside out, a bag with a somewhat differently formed flat bottom structure is provided. Another method of suitably shaping the bag element to provide a flat bottom includes the strategic separation of the walls of the bag element near its seamed and Other objects and advantages of the present invention and its details of construction will be apparent from a consideration of the following specification and accompanying drawings wherein:

FIG. I is a schematic isometric view showing a method of forming, in a continuous operation, a bag element embodying the principles of the present invention;

FIG. 2 is an enlarged cross-sectional view taken along reference line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary view of a portion of the bagelement of FIG. 1;

FIG. 4 is an enlarged isometric fragmentary view of the bag element of FIG. 1 showing a method of shaping the seamed end thereof to provide a flat bottom;

FIG. 5 is a view like FIG. 4 only showing a portion of the flat bottom as shaped;

FIG. 6 is an isometric view of a bag including a flat bottom portion shaped by the method portrayed in FIGS 3 and 4;

FIG. 7 is an enlarged crosssectional view taken along reference line 7-7 of FIG. 6;

FIG. 8 is an isometric view of a bag including a flat bottom portion shaped by turning the bag element of FIG. 1 inside out and shaking out its folded edge portions; and

' FIG. 9 is an enlarged cross-sectional view taken along reference line 9-9 of FIG. 8.

Referring particularly to FIG. 1, there is shown a bag element 10 formed from a continuous tube 12 of heat-sealable material. Bag element 10, when properly shaped, is useful to provide a square or flat bottom bag as is explained more fully hereinafter.

Tube 12, in a generally collapsed, noninflated condition, is fed from roll stock 14 under and edgewise upwardly about folding mandrel 16 to nip rollers 18 and 20. Folding mandrel 16 assisted by nip rollers 18 and 20 longitudinally or laterally folds the edge portions 22 and 24 of tube 12 to a position upon the main body portion 26 thereof, the latter being defined between the longitudinal fold lines 28 and 30. The folded tube 12, with four overlying plies at its folded edge portions 22 and 24, and two overlying plies at locations therebetween like that shown in FIG. 2, is then intermittently heat sealed in the transverse direction by sealing bar 36 to form an end seam 38 extending across the width of folded tube 12, and securing together therealong its respective overlying twoand four-ply portions. A cutting means or knife 40 th.'.n parts the folded and sealed tube 12 in the transverse direction at a location remote from the end seam 38 to obtain a unit bag element 10. Actually the sealing bar 36 and knife 40 can perform their functions simultaneously with the sealing bar 36 forming the end seam 38 on an upcoming bag element 10, while knife 40 located adjacent to and downwardly therefrom separates folded tube 12 from the previously end sealed bag element 10.

Bag element 10 comprises a generally tubular body 42 including therein the folded edge portions 22 and 24, and can be described as defining between its longitudinal fold lines 28 and 30, a front wall or first wall 44, and a rear wall or second wall 46, disposed in superposed relationship with the first wall 44 and joined together therewith along the seam 38. The description of these portions as first and second walls will be seen as more aptly applied when bag element 10 is unfolded and shaped to provide a flat bottom bag. Bag element 10 also includes a closed or secured end 48 located adjacent seam 38, and an open end 50 located remote from seam 38 opposite closed end 48, and across which the overlying plies comprising bag element I0 remain unsecured to provide a fill opening 52.

The closed end 48 of bag element 10 can be readily shaped to provide a flat or square bottom bag as illustrated in detail hereinafter. For the purposes of description it is convenient to identify strategic locations or points on the bag element 10 to better illustrate the shaping step. Points A and B comprise points on closed end 48 defined at the terminating ends of the innermost edges 32 and 34 of edge portions 22 and 24. Point D is located on the first wall 44 of bag element 10 adjacent the fold line 30 as best illustrated in FIG. 2. Point F is located directly adjacent point D but is defined as being on the second wall 46. FIG. 3 shows the distinction between points D and F with line 53 indicating the defining edge of first wall 44 hidden from view by folded edge portion 24, and on which the point D lies. Specifically, as shown in FIG. 3, points D and F extend inwardly from seam 38 a distance X, which distance is approximately equal to the distance X representing the width of folded edge portion 24. Points C and E differ from points D and F only in that they are located adjacent the fold line 28 of bag element 10.

A method of shaping the closed end 48 of bag element is illustrated in FIGS. 4 and 5. Here the first wall 44 and second wall 46 areseparately grasped by hands 54 and 56 at points D and F lying in adjacent relationship thereon, and sharply pulled apart to the position illustrated in FIG. 5. As will be noticed in FIG. 4, the separating of the first wall 44 from second wall 46 in this manner results in the unfolding of the folded edge portion 24 at locations between the open end 50 and points D and'F, with the points D and F comprising two adjacent corners of the flat bottom formed. What in effect has transpired in the shaping step is the shifting of inner edge 34 of the folded edge portion 24 to a position in planar alignment with the linear path of seal 38 securing closed end 48. This shifting of the location of inner edge 34 results in the partial unfolding of the folded edge portion 24 as described above, allowing the bag element 10 to bloom out into a flat bottom structure. Folded edge portion 22 can be similarly unfolded to complete the formation of the desired flat bottom in bag element 10.

FIG. 6 illustrates a flat bottom bag 58 formed from the bag element 10 by shaping its closed end 48 as described above. Bag 58 includes a tubular body 60 having a fill opening 62 at its end portion 64 corresponding to open end 50 of bag element l0, and a flat bottom 66 located at its other end 68 or end corresponding to the closed end 48 of bag element 10.

With flat bottom 66 so formed, a front wall 70 and rear wall 72 are distinctly perceptible as defined wall portions of the tubular body 60 and comprise that portion of first wall 44 and second wall 46 of bag element 10 located between its open end 50 and the previously defined comers points C, D, E and F. Joining together the front wall 70 to the rear wall 72 are side panels 74 and 76 formerly that part of the folded edge portions 22 and 24 located between the open end 50 of bag element 10 and the above enumerated comer points C, D, E, and F.

Flat bottom 66 of bag 58 comprises the portions of bag element 10 located between the closed end 48 and points C, D, E, and F and in part includes rectangular end panels 78 and 80 formerly included as portions of the first and second walls 44 and 46. End panels 78 and 80 merge along their 'outer edges 110 and 108, defined between points C and D and E and F, with the front wall 70 and rear wall 72, and are joined together along their common inner edges 82 and 84 by seam 38.

Flat bottom 66 additionally includes triangularly shaped members 86 and 88 comprising the unfolded parts of the folded edge portions 22 and 24 of bag element 10. Triangular members 86 and 88 are of two-ply construction as shown in FIG. 7, and each include an inner ply 94 and an outer ply 96 overlying the inner ply 94 and integrally joined together therewith along their common interiorly extending edges 98 and 100, which as shown in FIG. 6 extend between the four comer points of flat bottom 66 and the points A and B located on seam 38. The inner plies 94 and outer plies 96 each include substantially commonly located side edges 90 and 92 extending between points C and E. and points D and F, respectively. With the outer plies 96 merging therealong with the side panels 74 and 76, and with inner plies 94 joined together therealong with the rectangular panels 78 and 80. The inner plies 94 of triangular members 86 and 88 are further joined together with rectangular panels 78 and 80 by and along their common portions on seam 38. Actually with seam 38 dividing the inner plies 94, they can be aptly considered as each comprising two separate triangular portions 102 and 104 abuttingly engaged and joined together along the path of seam 38 In FIG. 8 the bag 58 is shown turned inside out and consequently the triangular members 86 and 88 are located within the confines of the bag 58. In this arrangement the outer plies 96 of triangular member 86 and 88 can still correctly be termed the outer plies since even though they are now located with the confines of bag 58 they still are positioned over the inner plies 94.

Bag 58 as shown in the FIG. 7 drawing can be formed directly from bag element 10 by turning the bag element 10 inside out and shaking out the portion of the folded edge portions 22 and 24 located between the open end 50 and points C, D, E and FQWhen formed in this manner, the terminating or raw edges 106 of bag 58 located adjacent seam 38 are positioned within the confines of bag 58 as is clearly depicted in FIG. 9, thereby enhancing the overall appearance of the bag 58 and making it suitable for containing expensive articles and the like wherein the appearance of the bag is an important aspect in the merchandising of the article. By again revising or turning inside out the bag 58 of FIG. 8, the bag 58 of FIG. 6 is obtained.

For the flat bottom of bag 58 to be shaped properly it is important that the inner edges 32 and 34 of the folded edge portions 22 and 24 do not extend beyond the longitudinal centerline 49 of the bag element 10. If the edge portions are folded to a width extending beyond the longitudinal centerline 49 of the bag 10, the flat bottom 66 of bag 58 cannot form or shape properly. Also, to more perfectly form flat bottom 66 of bag 10, further shaping by hand can be employed, as, for example, by further hand shaping the triangular members 86 and 88.

The bags of the present invention can be made from most any flexible material which is of sufficient durability or toughness to withstand the shaping of the closed end 48 of the bag element 10 without tearing or otherwise failing in structure. For example only, and where heat sealing is desired to form seam 38, the bag element 10 can be constructed of such heat sealable thermoplastics as polystyrene, polypropylene, polyethylene, saran, rubber hydrochloride, and similar plastic film or sheet material fusible by the application of heat. Where sealing by heat is not an important consideration, other materials not having excellent heat sealable qualities as, for example, many of the regenerated cellulose plastic compositions can be employed to construct bag element 10. Sealing in these cases'can be accomplished by suitable adhesives, solvents or other sealing substances as would be most appropriate for the material selected for the bag. Also as suitable flexibility and durability are present. Here, where a heat seal' 38 is desired, it should be noted that seam 38 requires both the inner and outer surfaces of bag element 10 to have heat-sealable qualities although the inner and outer surfaces need not be heat fusible or compatible to each other.

While certain representative embodiments and details have been shown for the purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.

Accordingly, What I Claim ls:

l. The method of making a flat bottom bag which comprises longitudinally folding the edge portions of a generally collapsed flexible tube to a superposed position with the main body portion thereof and short of the longitudinal centerline of said tube, forming a seam across the width of said folded tube adjacent one end thereof, thereby securing together along said seam the overlying plies comprising said folded tube, and thereafter shaping the seamed end of said folded tube to form a bag having a flat bottom.

,2. The method of claim 1 wherein said flexible tube is continuous and including the additional step of parting said continuous tube in the transverse direction at a location remote from said seam prior to said shaping step.

ing out to the extent possible its folded edge portions.

5. The method of claim 1 wherein said shaping step comprises shifting the inner edges of said folded edge portions to a position in planar alignment with the linear path of said seam. 

1. The method of making a flat bottom bag which comprises longitudinally folding the edge portions of a generally collapsed flexible tube to a superposed position with the main body portion thereof and short of the longitudinal centerline of said tube, forming a seam across the width of said folded tube adjacent one end thereof, thereby securing together along said seam the overlying plies comprising said folded tube, and thereafter shaping the seamed end of said folded tube to form a bag having a flat bottom.
 2. The method of claim 1 wherein said flexible tube is continuous and including the additional step of parting said continuous tube in the transverse direction at a location remote from said seam prior to said shaping step.
 3. The method of claim 3 wherein said tube comprises a thermoplastic material and wherein said seam is formed by the application of heat to said folded tube.
 4. The method of claim 1 wherein said shaping step comprises turning said folded and sealed tube inside out and shaking out to the extent possible its folded edge portions.
 5. The method of claim 1 wherein said shaping step comprises shifting the inner edges of said folded edge portions to a position in planar alignment with the linear path of said seam. 